We are all basically social animals, ON A SMALL SCALE. Once you start looking at people you don't know, humans by nature start becoming xenophobic. Racism is the most convenient way to differentiate people, because a "black" looks different than a "white" or a "Hispanic." The concept of races, outside ethnography and anthropology, is just a fiction useful for making categories. If we eliminate the idea of races, we might start using nationalities again, or political ideologies. People will discriminate, and there isn't much that can be done about it.